In 1974 and 1975 the South African Railways placed one hundred Class 6E1, Series 5 electric locomotives in mainline service, numbered in the range from E1546 to E1645. It was designed and built by Union Carriage and Wagon in Nigel, Transvaal, with the electrical equipment supplied by the General Electric Company (GEC). One of them, E1600, was later withdrawn from revenue service and rebuilt to an experimental 25 kV AC locomotive. Apart from the narrower stirrup step below the side doors of Series 3 number E1345 and earlier locomotives, Series 3 to Series 5 locomotives are visually indistinguishable from each other.See also the Wikipedia article on the South African Class 6E1, Series 5.E1557 re-entered service in 2013 as Class 18E, Series 2 number 18-777 after being rebuilt. See the Wikipedia article on the South African Class 18E, Series 2.